Conserving Forests and Native Plants through Deer Management
The white-tailed deer is perhaps the most influential wildlife species in Pennsylvania’s forested ecosystems. When their population is out of balance with habitat, they impact state forests and parks by browsing tree seedlings, shrubs, and wildflowers beyond their capacity to reproduce, impacting the ability to sustain a healthy, fully functioning forest.
To accomplish its mission of conserving Pennsylvania’s forests, DCNR manages deer on its lands and promotes sustainable deer management on all commonwealth forest lands.
Deer Management Assistance Program
The Deer Management Assistance Program (DMAP), established by the Pennsylvania Game Commission, allows DCNR to promote forest regeneration by targeting the most vulnerable and severely impacted tracts for additional antlerless deer harvests.
DCNR’s goals for DMAP are to:
Promote a diverse, healthy natural habitat that supports wildlife diversity and healthy deer populations
Provide additional hunting opportunities
Establish and maintain regeneration to support sustainable forestry practices with minimal need for deer fencing
Promote a healthy, sustainable forest and native, wild plant communities
To meet these goals, DCNR will follow these objectives:
Increase the number of native plants that are indicators of a balanced deer population
Increase the number of regeneration sample plots adequately stocked
Decrease the number of plants browsed by deer
reduce the need to fence for successful forest regeneration
Maintain good hunter participation
How Does DCNR Decide Where to Place DMAP Areas?
DCNR foresters and biologists determine where to place DMAP areas based on numerous criteria. One source is deer impact data.
DCNR collects data using a sampling protocol that assesses forest conditions in response to deer abundance. Across 2.2 million acres of state forest land and 10,000 sample plots, DCNR staff are collecting data on these variables:
Percentage of plots with acceptable seedlings
Presence of native wild plants preferred by deer
Percentage of competing vegetation and site limitations
Percentage of species browsed
Foresters review this data to understand deer impacts in local forest districts. Other sources of information help determine DMAP decisions, such as:
Past regeneration successes or failures
Deer fencing needs
Current and future management activities
Sale of DMAP tags and hunter success rates
How Many Deer Should There be on State Forest?
There are many opinions about how many deer there should be on state forest land. While deer numbers can generate a lot of discussion, DCNR focuses its efforts on habitat conditions.
“Biological carrying capacity,” which refers to a forest’s ability to support deer while maintaining healthy habitat, can vary year to year.
Carrying capacity can change annually, seasonally, and across properties.
That is why on state forest lands, DCNR focuses its deer management activities on habitat conditions and collects forest health data to help determine DMAP enrollment.
Deer’s Impact on Habitat Conditions and Forest Growth
Establishing young forests enhances the mix of forest habitat and is good for other wildlife and overall forest health. Out-of-balance deer populations impact other wildlife and frustrate efforts to establish healthy, young forests.
Impacts to Other Wildlife
Over-browsing by deer alters the diversity and habitat for other forest mammals and birds. For example, acorns and other tree nuts, known as mast, fluctuate greatly from year to year and are an important food resource for many forest mammals and some birds, such as wild turkeys and blue jays. Competition for mast can cause a reduction in:
Other small mammals
This in turn, reduces the predator populations that feed on them, including:
In addition, over-browsing can eliminate the shrub layer and greatly reduce the diversity of forest-floor plant species. Many wildlife species utilize the shrub layer and feed on forest-floor plant species, such as:
Snow shoe hare
Some birds, such as ovenbirds and eastern towhees, nest and feed in the ground layer. Reduced cover increases nest predation and decreases the ability of birds to raise their young successfully.
Other species, such as Eastern wood-pewee, indigo bunting, and black-and-white warbler, which use the middle layer of forest vegetation, have declined in heavily browsed forests.
Impacts to Forest Growth
Because more light is able to reach the forest floor and trigger new growth, plant and tree populations tend to increase after forest disturbances such as:
This only occurs where deer impacts are low enough to allow this new growth to establish and flourish.
Excessive browsing of early forest regeneration can suppress certain tree species and promote the expansion of unpalatable or resilient species, further slowing the regeneration process.
By exhausting their major food source and obstructing forest regrowth, deer in high numbers can cause a forest’s ability to support future deer populations to decline.
The Bureau of Forestry recognizes the ecological importance and considerable influence of white-tailed deer on commonwealth forests, and is dedicated to maintaining a healthy forest plant community in balance with a healthy deer population.